Surface treatment method and apparatus for tape

ABSTRACT

A surface treatment method for a tape which treats a surface of a tape continuously traveling, comprising:
         rubbing surfaces of the traveling tape each other to surface-treat the tape.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a surface treatment method and an apparatus for a tape. Particularly, the present invention relates to a surface treatment method and an apparatus for a tape for polishing a magnetic layer surface of a magnetic tape having a magnetic layer formed on a nonmagnetic support.

2. Description of the Related Art

For a magnetic tape, a magnetic layer is generally provided on a nonmagnetic support, and the magnetic layer contains a binder and ferromagnetic powder dispersed in the binder. For the manufacture of this magnetic tape, the ferromagnetic powder is first mixed and dispersed with the binder, an additive and an organic solvent to produce a magnetic coating liquid, and the magnetic coating liquid is applied on the nonmagnetic support. The magnetic coating liquid is then dried to produce a magnetic tape original fabric with a wide width. The magnetic tape original fabric with a narrow width is manufactured by slitting the magnetic tape original fabric with the wide width into a required width such as 8 mm, ½ inch, and 1 inch or the like using a slitting apparatus referred to as slitter.

By the way, minute projections and attachment may be occurred on the surface of the magnetic layer in the manufacturing step of the magnetic tape. The projections and the attachment cause the occurrence of reading fault referred to as dropout when using magnetic tape products for a long period of time. Thereby, the projections and attachment of the surface of the magnetic layer are generally removed by polishing the surface of the magnetic layer of the magnetic tape. For example, in Patent Documents 1 to 4 (Japanese Patent Application Laid-open Nos. 6-52544, 8-180405, 8-203071, and 9-16951), the surface of a magnetic tape is polished by bringing a polish tape and a wrapping tape into contact with the magnetic tape. In Patent Documents 5, 6 (Japanese Patent Application Laid-open Nos. 7-205033 and 7-254147), a magnetic tape is polished by lapping a whetstone wheel or a felt roll with the magnetic tape. In Patent Document 7 (Japanese Patent Application Laid-open No. 2002-319127), a magnetic tape is cleaned by a sponge pad.

However, since the polishing member was a consumable supply, and was worn out by the use in Patent Documents 1 to 7, there was a problem that the polishing state of the surface of the magnetic tape became unstable or the polishing member had to be periodically exchanged.

There was a problem that the surface of the magnetic tape was hardly formed into a suitable surface state in Patent Documents 1 to 7. That is, when the polishing is insufficient, the incidence rate of dropout increases in the magnetic tape. On the contrary, when the polishing becomes excessive, the cleaning performance of a head with the magnetic tape is unfortunately reduced, and thereby, the polishing must be put in the suitable polishing range. However, since the polishing degree changed according to the kind (composition and thickness or the like of the magnetic layer) of the magnetic tape in Patent Documents 1 to 7, the polishing condition (the pressing force and quality or the like of the polishing member) had to be unfortunately set for every magnetic tape.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the problems as described above, and it is an object of the present invention to provide a surface treatment method and an apparatus for a tape which can save consumable supplies in the polishing treatment of the tape and can provide a suitable surface state.

In order to attain the object, according to a first aspect of the present invention, there is provided a surface treatment method for a tape which treats a surface of a tape continuously traveling, comprising: rubbing surfaces of the traveling tape each other to surface-treat the tape.

The present inventor obtained findings that the surfaces of the tape are surface-treated by suitable polishing by rubbing the surfaces of the traveling tape each other. The present inventor obtained findings that when the magnetic layers of the magnetic tape are particularly rubbed each other, granular components contained in the magnetic layer functions as an abrasive and thereby the surfaces of the tape can be certainly polished.

The present invention has been accomplished based on these findings. Since the surfaces of the traveling tape are rubbed each other, the surfaces of the tape can be polished. Since a polishing member is not used according to the present invention, consumable supplies in surface-treating are saved, and the cost for surface-treating can be reduced. In addition, the maintenance property can be improved.

According to a second aspect of the present invention, there is provided a surface treatment method for a tape as set forth in the first aspect of the present invention, wherein the tape is a magnetic tape including a support and a magnetic layer formed on a surface of the support. Since the granular components are contained in the magnetic layer of the magnetic tape, the magnetic layer works as the abrasive and a large surface treatment effect is obtained.

According to a third aspect of the present invention, there is provided a surface treatment method for a tape as set forth in any one of the first and second aspects of the present invention, wherein the same surfaces of the tape are rubbed each other. Since the same surfaces of the tape, i.e., the surfaces having same property conditions such as composition and surface roughness are rubbed each other according to the third aspect, excess or deficiency of polishing hardly occurs, and a suitable surface state can be always obtained.

According to a fourth aspect of the present invention, there is provided a surface treatment method for a tape as set forth in any one of the first to third aspect of the present invention, wherein tapes having a same width are rubbed each other with the tapes positioned in a width direction. Since the tapes having the same width are rubbed each other in the state where they are positioned in the width direction according to the fourth aspect, the entire surfaces of the tapes can be certainly rubbed each other to surface-treat the surfaces.

According to a fifth aspect of the present invention, there is provided a surface treatment method for a tape as set forth in any one of the first to fourth aspects of the present invention, wherein the tapes traveling on one line are rubbed each other.

According to a sixth aspect of the present invention, there is provided a surface treatment method for a tape as set forth in any one of the first to fourth aspects of the present invention, wherein the tapes traveling on another line are rubbed each other.

According to a seventh aspect of the present invention, there is provided a surface treatment method for a tape as set forth in any one of the first to sixth aspects of the present invention, further comprising: cleaning the surfaces of the rubbed tapes. Thereby, substances sticking to the rubbed tape can be removed.

In order to attain the object, according to an eighth aspect of the present invention, there is provided a surface treatment apparatus for a tape comprising: a traveling device which makes a tape travel continuously; and a rubbing device which rubs the traveling tapes each other.

According to the present invention, the surface of the tape can be polished by rubbing the surfaces of the traveling tapes each other, and the cost can be reduced and the maintenance property can be enhanced by saving the use of consumable supplies such as the polishing member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a constitution view showing a surface treatment apparatus for a tape of a first embodiment;

FIG. 2 is an enlarged view of a surface treatment part of FIG. 1;

FIG. 3 shows the relationship between surface treating times and a surface state;

FIG. 4 is a constitution view showing a surface treatment apparatus for a tape of a second embodiment;

FIG. 5 is a constitution view showing a surface treatment apparatus having a different constitution from that shown in FIG. 4; and

FIG. 6 is a constitution view showing a surface treatment apparatus for a tape of a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of a surface treatment method and an apparatus for a tape according to the present invention will be described with reference to the accompanying drawings. The embodiment described below will describe an example of a surface treatment apparatus of a high density magnetic tape for computer backup. However, the kind of the tape which is surface-treated is not limited thereto.

FIG. 1 is a constitution view schematically showing a surface treatment apparatus 10 of a first embodiment. The surface treatment apparatus 10 shown in FIG. 1 is an apparatus for surface-treating a surface of a magnetic layer side of a magnetic tape 12 in a prescribed polishing degree. The constitution of the magnetic tape 12 will be described later in detail. A magnetic layer containing ferromagnetic particles is formed on a surface of a belt-like nonmagnetic support. This magnetic tape 12 can be manufactured by forming a magnetic layer on the surface of the support by an applying method, a vacuum deposition method or the like, subjecting the magnetic layer to orientation treatment, drying treatment, surface treatment or the like, and slitting the magnetic tape into a prescribed width (for example, 12.65 mm). In FIG. 1, the magnetic tape 12 is set so that the magnetic layer becomes the upper surface thereof.

As shown in FIG. 1, the magnetic tape 12 is attached to a rewinding apparatus (not shown) with the magnetic tape 12 wound around a winding core 14 in a rolled state. The roll-shaped magnetic tape 12 is continuously sent out from the rewinding apparatus by driving a feed roller 18. The feed roller 18 is a roller for making the magnetic tape 12 travel. For example, a suction drum which is rotated with the magnetic tape 12 adsorbed on the surface is used. Other known feed device such as a pair of nip rollers which carry the magnetic tape 12 while holding the magnetic tape 12 may also be used as the feed roller 18.

The magnetic tape 12 rewound by the feed roller 18 is sent to a surface treatment part 20 while being guided by a guide roller 16.

The surface treatment part 20 is constituted by stationary rollers 22, 24, 26 and a move roller 28. The stationary rollers 22, 26 are arranged with a prescribed interval at an upper part in the apparatus, and are rotatably supported. By contrast, the stationary roller 24 is arranged below the stationary rollers 22, 26, and is rotatably supported.

The magnetic tape 12 is wound in the order of the stationary rollers 22, 24, 26, and travels while being guided by the stationary rollers 22, 24, 26. A flange which is not shown is provided at an end part in a width direction on each of the stationary rollers 22, 24, 26, and the magnetic tape 12 is positioned in the width direction by this flange.

The move roller 28 is arranged between the stationary rollers 22, 26 and the stationary roller 24. The move roller 28 is rotatably supported by a bearing (not shown) provided in a guide 30, and the bearing (not shown) is slidably supported in a transverse direction along the guide 30. The bearing of the move roller 28 is connected to a driving apparatus (for example, an air cylinder, a feed screw mechanism or the like) which is not shown, and is moved along the guide 30 by the driving apparatus. Thereby, the move roller 28 can be slidingly moved in the transverse direction. The move roller 28 can be pressed against the magnetic tape 12, and the pressing force (or the lapping amount of the magnetic tape 12) can be adjusted.

A flange which is not shown is provided at the end part of the move roller 28 in the width direction, and thereby the traveling magnetic tape 12 can be positioned in the width direction.

The move roller 28 is arranged at the same side (a right side of FIG. 1) with respect to the magnetic tape 12 between the stationary rollers 22, 24 (hereinafter, referred to as a magnetic tape 12X), and the magnetic tape 12 between the stationary rollers 24, 26 (hereinafter, referred to as a magnetic tape 12Y). Therefore, as shown in FIG. 1, the magnetic tape 12X can be brought into contact with the magnetic tape 12Y by moving the move roller 28 in the left direction.

In a state where the move roller 28 is separated from the magnetic tape 12Y (that is, a state where the magnetic tapes 12X, 12Y are separated), the feed roller 18 controls a line speed (for example, 400 m/min). In a state where the move roller 28 presses the magnetic tape 12Y, the feed roller 18 controls the tension (for example, 0 to 350 g) of the magnetic tape 12.

A cleaning unit 32 is provided at the subsequent stage of the surface treatment part 20. The cleaning unit 32 is an apparatus for removing powdery materials and dust or the like sticking to the surface of the magnetic tape 12 by a belt-like nonwoven cloth 34. The nonwoven cloth 34 is attached to a roller 36 in a state where the nonwoven cloth 34 is wound in a rolled state, and is rewound from the roller 36, and is wound around a roller 40 via a pressing roller 38. While the nonwoven cloth 34 travels in the traveling direction and opposite direction of the magnetic tape 12 in that case, the nonwoven cloth 34 is pressed against the surface of the magnetic tape 12 by the pressing roller 38. Thereby, the surface of the magnetic tape 12 can be wiped by the nonwoven cloth 34, and the surface of the magnetic tape 12 can be cleaned. The constitution of the cleaning unit 32 is not limited thereto, and the surface of the magnetic tape 12 needs only to be cleaned. For example, air may be injected onto the surface of the magnetic tape 12.

The cleaned magnetic tape 12 is guided by a guide roller 42, and is wound around a winding core 44 rotated synchronizing with the feed roller 18 in a winding apparatus which is not shown.

Next, the operation of the surface treatment apparatus for a tape 10 constituted as described above will be described based on FIGS. 2, 3. FIG. 2 is an enlarged side view of a part of the surface treatment part 20 of FIG. 1.

As shown in FIG. 2, the magnetic tape 12X continuously traveling downwardly and the magnetic tape 12Y continuously traveling upwardly slide in the surface treatment part 20. That is, the magnetic layer of the magnetic tape 12X and the magnetic layer of the magnetic tape 12Y are rubbed each other. Since granular components are contained in the magnetic layer, the magnetic layer works as an abrasive when the magnetic layers are rubbed each other. Thereby, the surface of the magnetic layer of the magnetic tape 12 has a surface state where the surface is polished by friction. Thereby, the surface of magnetic tape 12 can be polished.

Since, particularly in this embodiment, the surfaces of the same magnetic tape 12, i.e., the magnetic layers which have the same composition are rubbed each other, the surface of magnetic tape 12 is surface-treated in a suitable polishing degree.

FIG. 3 shows the relationship between surface treating times and a surface wear state of the magnetic tape 12. This relationship is obtained by a test repeatedly conducting the surface treatment in the surface treatment part 20 and measuring the wear state of the surface. The wear state is evaluated by AlFeSil wear which is the substitution value of head wear. For the product of magnetic tape 12, the quality in which the wear state is in a range of about 20 to 60 is required. It is because the incidence rate of the dropout is increased when the wear state exceeds this quality range, and the cleaning performance of the head is reduced when the wear state is less than the quality range.

Comparative Examples 1, 2 shown in FIG. 3 show a case where surface treatment is conducted using polishing members such as polish whetstones and polish tapes. The kind (the composition and thickness or the like of the magnetic layer) of the magnetic tape 12 is different in the Comparative Examples 1, 2. Examples 1, 2 show a case where the surface treatment is conducted in the surface treatment part 20 of the embodiment described above, and the kind of the magnetic tape 12 is different in Examples 1, 2.

As shown in FIG. 3, since the wear develops due to the increase in treating times in Comparative Examples 1, 2 using the polishing member is increased, the test must determine a suitable polish range. Since the polishing member is consumed by prolonged use in Comparative Examples 1, 2, it is necessary to exchange the polishing member periodically, and there is a problem that maintenance property is poor and cost is also high.

By contrast, Examples 1, 2 in which the surface treatment of the embodiment is conducted have a suitable quality range in one surface treatment. Even if the surface treating times are increased, Examples 1, 2 always have the suitable range, and have a characteristic that the quality is stabilized. Even when the kind of the magnetic tape 12 is changed, Examples 1, 2 have a characteristic that they can be put in the suitable quality range without depending on the surface treating times. Therefore, according to the embodiment, the surface of the magnetic tape 12 can be certainly put in the suitable quality range.

Since the magnetic tapes 12 are rubbed each other in the embodiment, the polishing member is unnecessary and consumable supplies are not generated. Therefore, the maintenance is easily conducted, and the cost can be reduced.

Furthermore, since the magnetic tape 12X and the magnetic tape 12Y are rubbed each other while positioning them in the width direction by the move roller 28 having the flange in the embodiment, the magnetic tape 12X, 12Y are slid in a state where the magnetic tape 12X coincides with the magnetic tape 12Y in the width direction. Therefore, since the entire surfaces of the magnetic tapes 12X, 12Y are slid, the entire surfaces of the magnetic tapes 12, 12Y can be certainly polished.

Although only the surface of the magnetic layer side of the magnetic tape 12 is surface-treated in the first embodiment described above, the surface treatment is not limited thereto, and the rear surface of the magnetic tape 12 may be polished.

FIG. 4 is a schematic view showing a constitution of a surface treatment apparatus of a second embodiment. A surface treatment apparatus shown in FIG. 4 is different from the surface treatment apparatus 10 of FIG. 1 in that the apparatus in FIG. 4 is provided with a surface treatment part 50 for a rear surface and a cleaning unit 62 for a rear surface.

The surface treatment part 50 for the rear surface is provided at the subsequent stage of the cleaning unit 32, and is constituted as in the surface treatment part 20. That is, the surface treatment part 50 is constituted by stationary rollers 52, 54, 56 and a move roller 58. The stationary rollers 52, 56 are arranged at a prescribed interval at the lower part in the apparatus, and are rotatably supported. By contrast, the stationary roller 54 is arranged above the stationary rollers 52, 56, and is rotatably supported.

The magnetic tape 12 is wound in the order of the stationary rollers 52, 54, 56, and travels while being guided by the stationary rollers 52, 54, 56. A flange which is not shown is provided at an end part in a width direction on each of the stationary rollers 52, 54, 56, and the magnetic tape 12 is positioned in the width direction by the flange.

The move roller 58 is arranged between the stationary rollers 52, 56 and the stationary roller 54. The move roller 58 is rotatably supported by a bearing (not shown) provided in a guide 60, and the bearing (not shown) is slidably supported in a transverse direction along the guide 60. The bearing of the move roller 58 is connected to a driving apparatus (for example, an air cylinder and a feed screw mechanism or the like) which is not shown, and is moved along the guide 60 by the driving apparatus. Thereby, the move roller 58 can be slidingly moved in the transverse direction; the move roller 58 can be pressed against the magnetic tape 12; and the pressing force (or the lapping amount of the magnetic tape 12) can be adjusted.

A flange which is not shown is provided at the end part of the move roller 58 in the width direction, and the magnetic tape 12 can be positioned in the width direction by the flange.

The move roller 58 is arranged at the same side (a right side of FIG. 4) with respect to the magnetic tape 12 (hereinafter, referred to as a magnetic tape 12α) between the stationary rollers 52, 54, and the magnetic tape 12 (hereinafter, magnetic tape 12β) between the stationary rollers 54, 56. Therefore, as shown in FIG. 4, the magnetic tape 12αcan be brought into contact with the magnetic tape 12β by moving the move roller 58 in the left direction. Thereby, the rear surfaces of the traveling magnetic tapes 12α, 12β can be rubbed each other, and the rear surface of the magnetic tape 12 can be polished.

The cleaning unit 62 is provided at the subsequent stage of the rear surface treatment part 50. The cleaning unit 62 is an apparatus for removing powdery materials and dust or the like sticking to the rear surface of the magnetic tape 12 by a belt-like nonwoven cloth 64. The nonwoven cloth 64 is attached to a roller 66 in a state where the nonwoven cloth 64 is wound in a rolled state, is rewound from the roller 66, and is wound by a roller 70 through a pressing roller 68. While the nonwoven cloth 64 travels in the traveling direction and opposite direction of the magnetic tape 12 in that case, the nonwoven cloth 64 is pressed against the rear surface of the magnetic tape 12 by the pressing roller 68. Thereby, the rear surface of the magnetic tape 12 can be wiped by the nonwoven cloth 64, and the rear surface of the magnetic tape 12 can be cleaned.

The cleaned magnetic tape 12 is guided by guide rollers 72, 72, and is wound around the winding core 44 of a winding apparatus which is not shown.

Since the surface treatment part 50 for the rear surface is provided according to the second embodiment constituted as described above, the rear surface of the magnetic tape 12 can also be polished. Since the rear surfaces are rubbed each other in the same condition also in this case, the rear surface of the magnetic tape 12 can be put in the suitable quality range.

Although the surface treatment part 20 for the surface and the surface treatment part 50 for the rear surface are separately provided in the embodiment described above, the embodiment may not be limited thereto. For example, as shown in FIG. 5, there may be provided a surface treatment part 76 in which the surface and rear surface of the magnetic tape 12 are simultaneously surface-treated. In this surface treatment part 76, while the surfaces of the magnetic tapes 12, 12 are rubbed each other by the move roller 28, the rear surfaces of the magnetic tapes 12, 12 are rubbed each other by the move roller 58. The apparatus can be miniaturized by such apparatus constitution.

Although the first and second embodiments described above are examples in which the treating times of the surface and rear surface of the magnetic tape 12 are one time; the treating times are not limited thereto; and may be multiple times.

Although the magnetic tapes 12 traveling at the same speed are rubbed each other in the first and second embodiments described above, the magnetic tapes 12 traveling at the different speed may be rubbed each other.

Although the above first and second embodiments having the line constitution only for polish treatment are described, the other treatment step, for example, application treatment, dry treatment, slitting treatment or the like may be provided in the same line.

Although the magnetic tapes 12 traveling in the same line are rubbed each other in the first and second embodiments described above, the embodiments are not limited thereto, and the magnetic tapes 12 in another line may be rubbed each other.

FIG. 6 is a constitution view showing a surface treatment apparatus of a third embodiment. The surface treatment apparatus shown in FIG. 6 is an example in which the magnetic tapes in another line are rubbed each other to conduct the surface treatment, and is provided with two lines 80, 90. That is, there are provided an upper line 80 for making a magnetic tape 82 travel and a lower line 90 for making another magnetic tape 92 travel.

In the upper line 80, the magnetic tape 82 wound around a winding core 84 at the left side of FIG. 6 travels in the right direction. After the magnetic tape 82 is guided by guide rollers 86, 86, the magnetic tape 82 is rewound around the winding core 88. After the magnetic tape 92 wound around a winding core 94 at the right side of FIG. 6 travels in the left direction, and is guided by guide rollers 96, 96 in the lower line 90, the magnetic tape 92 is rewound around the winding core 98.

The guide rollers 86, 86 of the upper line 80 are arranged at a fixed interval. Similarly, the guide rollers 96, 96 of the lower line 90 are arranged at a fixed interval, and are respectively arranged below the guide rollers 86, 86.

A pressing roller 100 is provided between the guide rollers 86, 86. This pressing roller 100 presses the upper magnetic tape 82 downwardly by its own weight or a pressing device (cylinder or the like) which is not shown, and thereby the upper magnetic tape 82 and the lower magnetic tape 92 are rubbed each other.

Since the lower surface of the magnetic tape 82 and the upper surface of the magnetic tape 92 are rubbed each other according to the surface treatment apparatus constituted as described above, the lower surface of magnetic tape 82 and the upper surface of the magnetic tape 92 can be simultaneously surface-treated.

Although it is preferable that the surface (magnetic layer surface) of the magnetic tape 82 and the surface (magnetic layer surface) of the magnetic tape 92 are rubbed each other, or the rear surface of the magnetic tape 82 and the rear surface of the magnetic tape 92 are rubbed each other in the surface treatment apparatus of FIG. 6, the surface of the magnetic tape 82 and the rear surface of the magnetic tape 92, or the rear surface of the magnetic tape 82 and the surface of the magnetic tape 92 may be rubbed each other.

Furthermore, it is preferable that the magnetic tapes 82, 92 is the same kind (that is, the magnetic layer, the support, and the composition and thickness of the backcoat layer or the like are equal) in the above surface treatment apparatus, and it is particularly preferable that the magnetic layer has the same composition.

In the above surface treatment apparatus, the traveling speeds of the magnetic tapes 82, 92 can be set to any value. That is, the relative speed of the magnetic tape 82 and magnetic tape 92 can be freely set. The magnetic tapes 82, 92 may travel in the same direction, and in this case, the magnetic tape 82 and the magnetic tape 92 may travel at a different speed.

Although two lines 80 and 90 are provided in FIG. 6, the lines of three or more may be provided; the magnetic tapes of three or more may be simultaneously rubbed each other; and the magnetic tapes of three or more may be simultaneously surface-treated.

Hereinafter, the constitution of the magnetic tape surface-treated in the present invention will be described in detail. The magnetic tape is composed of a nonmagnetic support, a magnetic layer provided on the support, and a backcoat layer (simply referred to as back layer) provided at the opposite side of the magnetic layer if needed. The magnetic layer includes a ferromagnetic micropowder, powder components such as carbon black, abrasives and powder lubricants if needed, and a binder in which the powder components are dispersed. The backcoat layer includes the same composition as that of the magnetic layer except using the nonmagnetic powder instead of the ferromagnetic micropowder. The binder includes a resin component and a curing agent blended if needed.

First, the nonmagnetic support will be described. The nonmagnetic support used in the present invention is not specifically limited. The thickness thereof ranges from about 5 to 10 μm, with a thickness of about 6 to 9 μm being particularly preferable. Further, Young's modulus in the width direction ranges from 700 to 1,000 kg/mm², with 1,200 kg/mm² or more being particularly preferable. Further, Young's modulus in the longitudinal direction ranges from 400 to 1,200 kg/mm², with 450 to 1000 kg/mm² being preferable.

Examples of materials which are used as the nonmagnetic support include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; vinyl resins such as polyvinyl chloride; and plastics such as polycarbonate, polyimide, polyamide and polysulfone. Among them, polyethylene terephthalate, polyethylene naphthalate, polyamide and polyimide are preferably used. Polyethylene naphthalate (PEN) is particularly preferably used. Prior to coating, these supports may be subjected to corona discharge treatment, plasma processing, undercoating, heat treatment, dust removal treatment, metal vapor deposition, alkali treatment, or the like. These supports are described in, for example: West German Patent Publication No. 3,338,854; Japanese Patent Application Laid-open No. 59-116926; U.S. Pat. No. 4,388,368; and Sachio Mitsuishi, “Fibers and Industry”, Vol. 31, pp. 50 to 55 (1975). The center line average surface roughness of these supports preferably ranges from 0.001 to 0.5 μm (cutoff value 0.25 mm).

The above-described polyethylene naphthalate which is used in the present invention comprises a polyester composition that does not cause the polyethylene naphthalate to lose its fundamental properties, such as ethylene-2,6-naphthalene dicarboxylate homopolymer, a copolymer comprising 70 weight percent or more of repeating units in the form of ethylene-2,6-naphthalene dicarboxylate, and a mixture of these and another polymer (where the amount of the PEN is 70 weight percent or more). The PEN is a polymer having film-forming capabilities.

The PEN film which is used in the present invention can be manufactured by biaxial orientation of nonoriented film. For example, when employing sequential biaxial orientation, the first stage of drawing is conducted at an elevated temperature exceeding the glass transition temperature of the PEN, preferably by 3 to 10° C., and the second stage of drawing is conducted at a temperature identical to, or exceeding by up to 10° C., the first stage orientation temperature. The drawing factor is at least 2 in one axial direction, preferably equal to or higher than 2.5, and the surface area factor is equal to or higher than sixfold, preferably equal to or higher than eightfold. Heat treatment (heat setting) is preferably conducted at 170° C. or greater, more preferably 190° C. or more, under tension. The upper limit of the heat treatment temperature also depends on the treatment period, but must be a temperature at which a film will form in a stable shape. The heat treatment period may be from several seconds to several tens of seconds, with 3 to 30 seconds preferred. Subsequently, sequential drawing is preferably conducted to 1.05 to 2.5 fold in the longitudinal direction and 1.05 to 2.5 fold in the transverse direction at a temperature ranging from 10° C. below the glass transition point to 40° C. below the melting point, with another heat treatment being preferably conducted at a temperature ranging from 50° C. below the glass transition point to 10° C. below the melting point.

The ferromagnetic powder used in the magnetic layer of the present invention is not specifically limited, but the use of a ferromagnetic metal powder comprising Fe, Co, or Ni leads to remarkable effects. Among these, a ferromagnetic metal micropowder such as α—Fe, Co, Ni, Fe—Co alloy, Fe—Co—Ni alloy, Fe—Co—Ni—P alloy, Fe—Co—Ni—B alloy, Fe—Ni—Zn alloy, Ni—Co alloy, or Co—Ni—Fe alloy is preferred.

The shape of these ferromagnetic metal powders is not specifically limited, but an acicular, granular, cubic, rice-particle shaped, or plate-shaped powder is normally used. The particle size is, for acicular particles, a major axis length of 0.05 to 0.5 μm, preferably 0.05 to 0.3 μm, and particularly preferably 0.10 to 0.25 μm. The ratio of the major axis length/minor axis length ranges from 2/1 to 25/1, preferably from 3/1 to 15/1, and particularly preferably from 4/1 to 12/1. For plate-shaped particles, the plate diameter ranges from 0.02 to 0.20 μm, preferably from 0.03 to 0.10 μm, particularly preferably from 0.04 to 0.07 μm, and the plate diameter/plate thickness ratio ranges from 1/1 to 30/1, preferably from 2/1 to 10/1, and still more preferably from 2.5 to 7/1.

The specific surface area (SBET) of these ferromagnetic metal powders ranges from 47 to 80 m²/g, more preferably from 53 to 70 m²/g. The coercivity (Hc) ranges from 1250 to 2500 Oe. The saturation magnetization (σS) ranges from 100 to 180 emu/g, preferably from 110 to 150 emu/g. The moisture content preferably ranges from 0.1 to 2.0 weight percent, and the pH preferably ranges from 3 to 11 (5 g of ferromagnetic powder/100 g of water). The surface of the ferromagnetic metal powder may, based on the respective objective, have a rust-preventing agent, surface treatment agents, dispersant, lubricant, antistatic agent or the like described further below that is adsorbed by immersion in solvent prior to dispersion.

The metal component of the ferromagnetic metal powder comprises 60 weight percent or more, with 70 weight percent or more of the metal component being comprised of at least one ferromagnetic metal powder or alloy (such as Fe, Fe—Co, Fe—Co—Ni, Co, Ni, Fe—Ni, Co—Ni, and Co—Ni—Fe). Iron carbide, iron nitride, or another alloy which may comprise some other components (such as Al, Si, S, Sc, Ti, V, Cr, Mn, Cu, Zn, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Hg, Pb, Bi, La Ce, Pr, Nd, B, and P) may be used in a range equal to or less than 30 weight percent, preferably equal to or less than 20 weight percent, of the metal component. To supplement the strength of the metallic iron, the addition of Al, Si, and Cr, either singly or in combination, to the outer layer is preferable. The above-described ferromagnetic metal powder may also comprise a small quantity of hydroxides, oxides, alkali metal elements (Na, K, or the like), and alkaline earth metal elements (Mg, Ca, Sr). Methods of manufacturing these ferromagnetic metal powders are already known and may be used to manufacture the ferromagnetic metal powder which is a typical example of the ferromagnetic metal powder used in the present invention.

The following are specific examples of methods of manufacturing ferromagnetic metal powders used as the ferromagnetic powder in the present invention. (a) Reduction of a complex organic acid salt (chiefly oxalates) with a reducing gas such as hydrogen. (b) Reduction of iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe—Co particles. (c) Thermal decomposition of a metal carbonyl compound. (d) Reduction by addition of a reducing agent such as sodium boron hydride, hypophosphite, or hydrazine to the aqueous solution of a ferromagnetic metal. (e) The use of a mercury cathode to precipitate a ferromagnetic metal powder by electrolysis, followed by separation from the mercury. (f) The vaporization of a metal in an inert gas and under low pressure to obtain micropowder.

Plate-shaped hexagonal barium ferrite may also be used as ferromagnetic powder used in the present invention. The barium ferrite has a particle size with a diameter ranging from about 0.001 to 1 μm and a thickness ranging from about ½ to 1/20 of the diameter. The specific gravity of barium ferrite ranges from about 4 to 6 g/cc and its specific surface area ranges from 1 to 70 m²/g. As necessary, FeOx (X=1.33 to 1.50), Co-containing FeOx or the like may also be used.

Examples of the nonmagnetic powders which may be used in the backcoat layer provided as needed in the present invention include various powders such as those disclosed in Japanese Patent Application Laid-open No. 59-110038. That is, examples of various powders include carbon black, graphite, tungsten disulfide, boron nitride, silicon dioxide, calcium carbonate, aluminum oxide, iron oxide, titanium dioxide, magnesium oxide, zinc oxide, calcium oxide, lithopone, talc, and stannic oxide.

Examples of resin components of binders which are used in the magnetic layer and backcoat layer of the present invention include conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron-beam curing resins, ultraviolet curing resins, visible light curing resins, and mixtures thereof.

The thermoplastic resins used preferably have softening temperatures equal to or less than 150° C., number average molecular weights of 10,000 to 300,000, and degrees of polymerization of about 50 to 2,000, more preferably about 200 to 600. Examples which are used include vinyl chloride-vinyl acetate copolymers, vinyl chloride polymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic ester-acrylonitrile copolymers, acrylic ester-vinylidene chloride copolymers, acrylic ester-styrene copolymers, methacrylic ester-acrylonitrile copolymers, methacrylic ester-vinylidene chloride copolymers, methacrylic ester-styrene copolymers, urethane elastomers, nylon-silicon resins, nitrocellulose-polyamide resins, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymers, butadiene-acrylonitrile copolymers, polyamide resins, polyvinylbutyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, ethyl cellulose, methyl cellulose, propyl cellulose, methyl ethyl cellulose, carboxymethyl cellulose, acetyl cellulose, or the like), styrene-butadiene copolymer, polyester resin, polycarbonate resin, chlorovinylether-acrylic ester copolymers, amino resins, various synthetic rubber thermoplastic resins, and mixtures thereof.

Thermosetting resins and reactive resins have a molecular weight of 200,000 or less in the coating liquid and can be heated and wetted following coating and drying to subject them to reactions such as condensation and addition to obtain compounds of an infinite molecular weight. Of these, compounds which do not soften or melt prior to the thermal decomposition of the resin are preferable. Specific examples of the compounds include phenol resins, phenoxy resins, epoxy resins, polyurethane resins, polyester resins, polyurethane polycarbonate resins, urea resins, melamine resins, alkyd resins, silicon resins, acrylic reactive resins (electron beam cured resins), epoxy-polyamide resins, nitrocellulose melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanates, polyamine resins, polyimine resins, and mixtures thereof.

One to six members from among the group consisting of carboxylic acid (COOM), sulfinic acid, sulfenic acid, sulfonic acid (SO₃M), phosphoric acid (PO(OM)(OM)), phosphonic acid, sulfuric acid (OSO₃M), acid groups thereof such as ester groups (M denoting H, an alkali metal, an alkaline earth metal, or a hydrocarbon group), amino acids, aminosulfonic acids, sulfuric acid and phosphoric acid esters of amino alcohols, amphoteric groups such as alkyl betaines, amino groups, imino groups, imido groups, amide groups, hydroxyl groups, alkoxyl groups, thiol groups, alkylthio groups, halogen groups (F, Cl, Br, I), silyl groups, siloxane groups, epoxy groups, isocyanate groups, cyano groups, nitryl groups, oxo groups, acryl groups, and phosphine groups are incorporated as functional groups other than main functional groups into the thermoplastic resin, thermosetting resin, or reactive resin, with from 1×10⁻⁶ to 1×10⁻² equivalent of functional groups preferably being present per gram of resin.

As the curing agent, a polyisocyanate compound is usually used. Examples of polyisocyanate compounds which are used in the magnetic layer and backcoat layer of the present invention include isocyanates such as tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate and isophorone diisocyanate, products of these isocyanates and polyalcohols, dimmer to decamer of polyisocyanates produced by condensation of isocyanates, and products of triisocyanates and polyurethane having an isocyanate as terminal functional group. The average molecular weight of these polyisocyanates preferably ranges from 100 to 20,000. These isocyanates are commercially available under the following trade names, for example: Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR and Millionate MTL (manufactured by Nippon Polyurethane Industry Co. Ltd.); Takenate D-102, Takenate D-110N, Takenate D-200, Takenate D-202, Takenate 300S, and Takenate 500 (manufactured by Takeda Chemical Industries Co. Ltd.); Sumidule T-80, Sumidule 44S, Sumidule PF, Sumidule L, Sumidule N, Desmodule L, Desmodule IL, Desmodule N, Desmodule HL, Desmodule T65, Desmodule 15, Desmodule R, Desmodule RF, Desmodule SL, and Desmodule Z4273 (manufactured by Sumitomo Bayer Co. Ltd.). They can be used singly or in combinations of two or more by exploiting differences in curing reactivity. To promote the curing reaction, compounds having hydroxyl groups (butanediol, hexanediol, polyurethane having a molecular weight of 1,000 to 10,000, water, or the like) and amino groups (monomethylamine, dimethylamine, trimethylamine, or the like) as well as catalysts in the form of metal oxides may also be used together. These compounds having hydroxyl groups or amino groups are preferably polyfunctional. The polyisocyanates are preferably used in a proportion of 2 to 70 weight parts per 100 weight parts of the total quantity of binder resin and polyisocyanates combined in the magnetic layer and the backcoat layer, with the use of 5 to 50 weight parts being more preferred. Specific examples are described in Japanese Patent Application Laid-open Nos. 60-131622 and 61-74138.

These binders are used singly or in combination, and in addition, an additive is added. For the mixed rate of the ferromagnetic powder of the magnetic layer and binder, the binder is used in a range of 5 to 300 weight parts per 100 weight parts of the ferromagnetic powder. For the mixed rate of the powder of the backcoat layer and binder, the binder is used in a range of 8 to 400 weight parts per 100 weight parts of the powder. As additives, carbon black, abrasives, lubricants, dispersants, dispersion adjuvants, antimildew agents, antistatic agents, antioxidants, and solvents or the like are added.

Examples of types of carbon black used in the present invention include furnace black for rubber, thermal for rubber, black for coloring, and acetylene black. These carbon blacks are used in the tape with the objectives of preventing static electricity, blocking light, controlling the coefficient of friction, and increasing durability. Specific examples of abbreviations of carbon black used in the United States include SAF, ISAF, IISAF, T, HAF, SPF, FF, FEF, HMF, GPF, APF, SRF, MPF, ECF, SCF, CF, FT, MT, HCC, KCF, MCF, LFF, and RCF; those classified under U.S. ASTM standard D-1765-82a may be used. The average particle size of these carbon blacks which are used in the present invention ranges from 5 to 1,000 nm (electron microscope), the specific surface area thereof as measured by nitrogen adsorption ranges from 1 to 800 m²/g, the pH ranges from 4 to 11 (JIS Standard K-6221-1982), and the dibutyl phthalate (DBP) oil absorption capacity ranges from 10 to 800 mL/100 g (JIS Standard K-6221-1982). For the size of the carbon black used in the present invention, to lower the surface electrical resistivity of the coating film, carbon black with a particle diameter of 5 to 100 nm can be used, and when controlling the strength of the coating film, carbon black with a particle diameter of 50 to 1,000 nm can be used. To control the surface roughness of the coating film, smaller microgranular carbon black (smaller than 100 nm) is used for smoothing to reduce spacing loss. To reduce the coefficient of friction by roughening the surface of the coating film, coarse granular carbon black (100 nm or larger) is used. The type and quantity of carbon black which is added is thus different depending on the objectives required in the magnetic recording medium.

The carbon black can be further surface treated with a dispersant or the like, described further below, or grafted with resin for use. Carbon black a portion of which has been converted to graphite by setting the temperature of the furnace when manufacturing carbon black to 2,000° C. or above may also be used. Further, as a form of special carbon black, hollow carbon black may also be used.

These types of carbon black are desirably used in the magnetic layer in a proportion of 0.1 to 30 weight parts, per 100 weight parts of ferromagnetic powder. In the backcoat layer, 20 to 400 weight parts are preferably used per 100 weight parts of binder. For example, “the Carbon Black Handbook” compiled by the Carbon Black Association (published in 1971) may be consulted for types of carbon black which can be used in the present invention. Examples of these carbon blacks are disclosed in U.S. Pat. Nos. 4,539,257 and 4,614,685 as well as Japanese Patent Application Laid-open Nos. 61-92424 and 61-99927.

In the present invention, abrasives are used to improve the durability of the magnetic recording medium and improve the head cleaning effect in VCRs. The abrasives are materials generally having a polishing or burnishing effect. Examples include materials chiefly having a Mohs'hardness equal to or higher than 6, preferably equal to or higher than 8, such as α-alumina, γ-alumina, α, γ-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, cotraveldum, artificial diamond, α-iron oxide, garnet, emery (chiefly comprised of cotraveldum and magnetite), garnet, silica rock, silicon nitride, boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, quartz, tripoli, diatomaceous earth and dolomite in combinations of 1 to 4 metarials. The average particle size of these abrasives preferably ranges from 0.005 to 5 μm, particularly preferably from 0.01 to 2 μm. These abrasives are added to the magnetic layer in a range of 0.01 to 20 weight parts per 100 weight parts of the ferromagnetic powder. The abrasives are desirably used in a proportion of 0.01 to 5 weight parts, per 100 weight parts of binder described further below, in the backcoat layer. Specific examples of the abrasives include AKP/1, AKP15, AKP20, AKP30, AKP50, AKP80, Hit50, and Hit100 manufactured by Sumitomo Chemical Co., Ltd. These are described in Japanese Examined Application Publication No. 52-28642.

Examples of powdered lubricants which are used in the present invention include inorganic micropowders such as graphite, molybdenum disulfide, boron nitride, graphite fluoride, calcium carbonate, barium sulfate, silicon oxide, titanium oxide, zinc oxide, tin oxide, and tungsten disulfide; and resin micropowders such as acryl styrene resin micropowder, benzoguanamine resin micropowder, melamine resin micropowder, polyolefin resin micropowder, polyester resin micropowder, polyamide resin micropowder, polyimide resin micropowder, and polyethylene fluoride resin micropowder.

Examples of organic compound lubricants which can be used include compounds incorporating fluorine or silicon such as silicone oils (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane, fluoroalkyl polysiloxane (KF96 and KF 69 manufactured by Shin-Etsu Chemical Co., Ltd. or the like)), fatty acid-modified silicone oils, fluoroalcohols, polyolefins (polyethylene waxes, polypropylene, or the like), polyglycols (ethylene glycol, polyethylene oxide wax, or the like), tetrafluoroethyleneoxide wax, polytetrafluoroglycol, perfluoroalkylether, perfluorofatty acids, perfluorofatty acid esters, perfluoroalkyl sulfuric acid esters, perfluoroalkyl sulfonic acid esters, perfluoroalkylbenzene sulfonic acid esters and perfluoroalkyl phosphoric acid esters, organic acid and organic acid ester compounds such as alkyl sulfuric acid esters, alkyl sulfonic acid esters, alkyl phosphonic acid triesters, alkyl phosphonic acid monoesters, alkyl phosphonic acid diesters, alkyl phosphoric acid esters and succinic acid esters, nitrogen and sulfur-comprising heterocyclic compounds such as triazaindolizine, tetraazaindene, benztriazole, benzdiazole and EDTA, fatty acid esters comprising a monobasic fatty acid having 10 to 40 carbon atoms and one or more monohydric alcohols, dihydric alcohols, trihydric alcohols, tetrahydric alcohols, or hexahydric alcohols having 2 to 40 carbon atoms, fatty acid esters comprising a monobasic fatty acid having 10 or more carbon atoms and a monohydric to hexahydric alcohol having a total number of carbon atoms including those of the monobasic fatty acid of 11 to 70, fatty acid having 8 to 40 carbon atoms or fatty acid amides, fatty acid alkylamides, or aliphatic alcohols.

Specific examples of these compounds include butyl caprylate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, ethyl palmitate, butyl palmitate, octyl palmitate, 2-ethylhexyl palmitate, ethyl stearate, butyl stearate, isobutyl stearate, octyl stearate, 2-ethylhexyl stearate, amyl stearate, isoamyl stearate, 2-ethylpentyl stearate, 2-hexyldexyl stearate, isotridecyl stearate, amide stearate, alkylamide stearate, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, oleyl oleate, oleyl alcohol, lauryl alcohol, montan wax, and carnauba wax. They may be used singly or in combination.

In the present invention, lubricating oil additives may also be used singly or in combination as lubricants. Examples of lubricants include antioxidants known as rust preventing agents (other metal chelating agents such as alkyl phenol, benzotriazine, tetraazaindene, sulfamide, guanidine, nucleic acids, pyridine, amines, hydroquinone and EDTA), rust stopping agents (naphthenic acid, alkenyl succinate, phosphoric acid, dilauryl phosphate or the like), oily agents (rapeseed oil, lauryl alcohol, or the like), extreme pressure agents (dibenzylsulfide, tricresyl phosphate, tributyl phosphite, or the like), detergent dispersants, viscosity index increasing agents, fluidity point decreasing agents, and antifoaming agents. These lubricants can be used in a range of 0.01 to 30 weight parts per 100 weight parts of binder.

Examples of dispersants and dispersion adjuvants which are used in the present invention include fatty acids having 2 to 40 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linolic acid, linolenic acid, stearolic acid, behenic acid, maleic acid, and phthalic acid (R1COOH, where R1 denotes an alkyl group, phenyl group, or aralkyl group having 1 to 39 carbon atoms); metallic soaps (copper oleate) comprising alkali metal (Li, Na, K, or the like) or alkaline earth metal (Mg, Ca, Ba, or the like) of the above fatty acids, NH4⁺, Cu, Pb, or the like; fatty acid amides; and lecithin (soybean oil lecithin). Further compounds which can also be used are higher alcohols (butanol, octyl alcohol, myristyl alcohol, stearyl alcohol) having 4 to 40 carbon atoms; sulfuric acid esters of the same; sulfonic acid; phenyl sulfonate; alkyl sulfonate; sulfonic acid ester; phosphoric acid monoester; phosphoric acid diester; phosphoric acid triester; alkyl phosphonate; phenyl phosphonate; and amine products. Further, polyethylene glycol, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid metal salts, sulfosuccinic acid esters, or the like may also be used. These dispersants are usually used singly or in combination. A single dispersant is added in a range of 0.005 to 20 weight parts per 100 weight parts of binder. These dispersants may be precoated on the surface of the ferromagnetic powder or nonmagnetic powder or added during dispersion. Such dispersants and dispersant adjuvants are described, for example, in Japanese Examined Application Publication Nos. 39-28369, 44-17945, and 48-15001, as well as U.S. Pat. Nos. 3,387,993 and 3,470,021.

In the present invention, an antimildew agent may be used in the form of 2-(4-thiazolyl)benzimidazole, N-(fluorodichloromethylthio)phthalimide, 10,10′-oxybisphenoxarsine, 2,4,5,6-tetrachloroisophthalonitrile, P-tolyldiiodomethylsulfone, triiodoallylalcohol, dihydroacetoacetic acid, mercury phenyloleate, bis(tributyltin) oxide, salicylanilide, or the like.

Antimildew agents listed above are described, for example, in “Microorganism Harm and Prevention Techniques”, 1972, Kogaku Tosho, and “Chemistry and Industry”, 32, 904 (1979). In the present invention, as antistatic agents other than carbon black, there are used electrically conductive powders such as graphite, denatured graphite, carbon black graphite polymer, tin oxide-antimony oxide, tin oxide and titanium oxide-tin oxide-antimony oxide; natural surfactants such as saponin; nonionic surfactants such as alkylene oxides, glycerin, glycidol, polyhydric alcohols, polyhydric alcohol esters and alkyl phenol EO adducts; cationic surfactants such as higher alkylamines, cyclic amines, hydantoin derivatives, amidoamines, esteramides, quaternary ammonium salts, pyridine and other heterocycles, phosphoniums and sulfoniums; anionic surfactants comprising acid group such as carboxylic acid, sulfonic acid, phosphonic acid, phosphoric acid, sulfuric acid ester groups, phosphonic acid esters and phosphoric acid ester groups; amino acids; aminosulfonic acids, sulfuric acid, phosphoric acid esters of amino alcohols, amphoteric surfactants such as alkyl betaine. These surfactants may be added singly or in combination. These surfactants are preferably added to the magnetic recording medium in a range of 0.01 to 10 weight parts per 100 weight parts of ferromagnetic powder, and to the backcoat layer in a range of 0.01 to 30 weight parts, per 100 weight parts of binder. Although these are used as antistatic agents, they may in some cases also be used to improve dispersion and magnetic characteristics, improve lubrication, as coating adjuvants, moistening agents, curing promoters, and dispersion promoters.

The magnetic layer may be formed by the usual methods. For example, there may be used a method of kneading and dispersing the above-described ferromagnetic powder, resin components, and, as needed, magnetic layer forming components such as abrasives and curing agents along with a solvent to prepare a magnetic coating liquid, and then applying the magnetic coating liquid on a nonmagnetic support. Examples of organic solvents which are used during the dispersion, kneading, and coating of the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone and tetrahydrofuran; alcohols such as methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol and methyl cyclohexanol; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate and glycol acetate monoethylether; ethers such as diethylether, tetrahydrofuran, glycol dimethylether, glycol monoethylether and dioxane; tars (aromatic hydrocarbons) such as benzene, toluene, xylene, cresol, chlorobenzene and styrene; chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene; N,N-dimethylformaldehyde; and hexane in any ratio. Two or more of these solvents are usually used in any ratio. Further, these organic solvents may comprise impurities (polymers of the solvent itself, moisture, starting material components, or the like) of a small quantity of 1 weight percent or less. These solvents are used in a range of 100 to 20,000 weight parts per 100 weight parts of the total solid component of the magnetic layer coating liquid, backcoat layer coating liquid, or undercoating liquid. The solid component ratio of the magnetic layer coating liquid preferably ranges from 10 to 40 weight percent. Further, the solid component ratio of the backcoat layer coating liquid preferably ranges from 5 to 20 weight percent. An aqueous solution (water, alcohol, acetone, or the like) may be used instead of an organic solvent.

The dispersion and kneading methods are not specifically limited. Further, the order in which individual components (resin, powder, lubricants, and solvent, or the like) are added, the spot in which they are added during dispersion and kneading, the dispersion temperature (0 to 80° C.), or the like may be suitably set. In the preparation of the magnetic layer coating liquid and backcoat layer coating liquid, usual kneaders may be used. Examples which can be used as a kneeler include a double roll mill, triple roll mill, ball mill, pebble mill, tron mill, sand polisher, Szegvari, Atliter, high-speed impellor, disperser, high-speed stone mill, high-speed impact mill, disper, kneader, high-speed mixer, ribbon blender, co-kneader, intensive mixer, tumbler, blender, disperser, homogenizer, single-screw extruder, twin-screw extruder, and ultrasound disperser. In usual dispersion and kneading, multiple dispersers and kneaders are used and processing is continuously conducted. Specifics of techniques relating to kneading and dispersion are described in T. C. Patton, “Paint Flow and Pigment Dispersion”, John Wiley & Sons (1964); Shinichi Tanaka, “Kogyo Zairyo”, Vol. 25, p. 37 (1977); and the references cited by these publications. To conduct efficient dispersion and kneading, as auxiliary materials, there may be used steel balls, steel beads, ceramic beads, glass beads and organic polymer beads with a corresponding spherical diameter of 0.05 mm to 10 cm. The materials are not limited to being spherical. The items described in U.S. Pat. Nos. 2,581,414 and 2,855,156 or the like may also be used. In the present invention, kneading and dispersion may be conducted in accordance with methods described in the above-cited publications and in references cited by these publications to prepare the magnetic coating liquid and the backcoat layer coating liquid.

Examples of methods which can be used in applying the magnetic coating liquid and the backcoat layer coating liquid on the support include preparing the viscosity of the coating liquid to 1 to 20,000 centistokes (25° C.) followed by the use of air doctor coating, blade coating, air knife coating, squeeze coating, immersion coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, spray coating, rod coating, positive rotation roll coating, curtain coating, bar coating, extrusion coating, and spin coating. Other methods may also be used. These methods are described in detail in “The Coating Industry”, pp. 253-277 (Asakusa Shoten, published Mar. 20, 1971).

The order in which these coating liquids are applied may be selected as desired. Further, an undercoated layer may be formed prior to applying a desired liquid, and corona discharge treatment may be applied to enhance adhesion to the support. Further, when the magnetic layer or the backcoat layer is of a multilayer configuration, the multiple layers may be simultaneously or sequentially applied. The specifics thereof are described in Japanese Patent Application Laid-open No. 57-123532 and Japanese Examined Application Publication No. 62-37451 or the like.

The magnetic coating liquid which has been applied by these methods to a thickness of about 1 to 200 μm on the support may be further subjected as needed to magnetic orientation in a desired direction (vertical, longitudinal, width, random, slanting, or the like) at about 500 to 5000 G in which the ferromagnetic powder in the layer is oriented while, as needed, the ferromagnetic powder is immediately subjected to multistages of drying at 20 to 130° C., and then formed magnetic layer is dried to have 0.1 to 30 μm in thickness. The conveyance rate of the support during this process usually ranges from 10 to 900 m/min, the drying temperature is controlled to 20 to 130° C. in multiple drying zones, and the quantity of residual solvent in the coating film is set to 0.1 to 40 mg/(½ inch)/m².

Following drying, calendering of the coated layers is conducted as needed. For example, super calender rolls or the like are used in calendering. Calendering reduces voids created by the removal of solvent during drying and increases the fill rate of ferromagnetic powder in the magnetic layer, thereby yielding a magnetic recording medium with good electromagnetic characteristics.

When a curing agent is used as the forming components of the binder in the stage where the calendering has been completed, 90 weight percent or more of the curing agent contained in the magnetic layer is usually present in unreacted form. Thus, it is preferable that a curing treatment is conducted to cause at least 50 weight percent (particularly preferably, 80 weight percent or more) of the curing agent to react, after which the next process is preferably performed. There are two types of curing treatments: heat curing treatments and electron beam curing treatments. In the present invention, either of these methods may be used. The curing treatment causes the unreacted curing agent contained in the calendered magnetic layer to react with, for example, resin components such as vinyl chloride copolymer and polyurethane resin to form a three-dimensional meshlike crosslinked structure. The procedures of heat treatment itself are known; heat treatment based on such methods may be used in the present invention. For example, the heating temperature is usually equal to or higher than 40° C. (preferably, within the range of 50 to 80° C.) and the heating period is usually equal to or longer than 20 hours (preferably, 24 hours to 7 days). Curing treatment based on electron-beam irradiation is also known; curing treatments based on such methods may be used in the present invention.

In the present invention, the magnetic recording medium thus manufactured is slitted in desired shape using a usual cutter such as a slitter on a usual condition, and wound on plastic or metal reels. In the present invention, for the surface of the magnetic layer, or surfaces of the magnetic layer and backcoat layer thus produced, the magnetic recording medium (the magnetic layer, the backcoat layer, the edge end face and the base surface) may be burnished with a polishing tape in a step immediately preceding winding or in an earlier step. The specifics of burnishing are described in Japanese Patent Application Laid-open No. 63-259830, for example.

Further, the magnetic recording medium is subjected to a wiping process to remove grime and excess lubricant from the surface of the magnetic recording medium. A nonwoven cloth is used to wipe the magnetic layer surface, backcoat layer surface, edge end face, back side base face. As the wiping material, there may also be used various Vilenes manufactured by Japan Vilene Company, Ltd., Toraysee and Exene manufactured by Toray Industries, Inc., Kuraray WRP series from Kuraray Co., Ltd., nonwoven cloth made of nylon, nonwoven cloth made of polyester, nonwoven cloth made of rayon, nonwoven cloth made of acrylonitrile, and mixed fiber nonwoven cloth. Tissue paper and Kim Wipes may also be used. The specifics of those are described in Japanese Patent Application Laid-open No. 1-201824. The wiping treatment completely removes substances and organic substances adhering to the magnetic layer and/or backcoat layer, thus permitting a reduction in dropout and in the frequency of clogging.

The magnetic recording medium is desirably manufactured by consecutively conducting the steps of preliminary processing and surface processing of powders; kneading and dispersion; coating, orientation, and drying; calendering; curing (thermosetting, radiation treatment (EB)); cutting; burnishing; wiping; and winding. In this field, the methods described in Japanese Examined Application Publication No. 41-13181 are considered basic and important techniques. However, the processing sequence is not limited to that described above.

The ferromagnetic powders, nonmagnetic powders, binders, additives (lubricants, dispersants, antistatic agents, surface treatment agents, carbon black, abrasives, light-blocking agents, antioxidants, antimildew agents, or the like), solvents, supports (may have an undercoated layer, a backcoat layer and a back undercoating), and methods of manufacturing magnetic recording media which are in the present invention may be referred to those described in Japanese Examined Application Publication No. 56-26890. 

1. A surface treatment method for a tape which treats a surface of a tape continuously traveling, comprising: rubbing surfaces of the traveling tape each other to surface-treat the tape.
 2. The surface treatment method for a tape according to claim 1, wherein the tape is a magnetic tape including a support and a magnetic layer formed on a surface of the support.
 3. The surface treatment method for a tape according to claim 1, wherein the same surfaces of the tape are rubbed each other.
 4. The surface treatment method for a tape according to claim 2, wherein the same surfaces of the tape are rubbed each other.
 5. The surface treatment method for a tape according to claim 1, wherein tapes having a same width are rubbed each other with the tapes positioned in a width direction.
 6. The surface treatment method for a tape according to claim 2, wherein tapes having a same width are rubbed each other with the tapes positioned in a width direction.
 7. The surface treatment method for a tape according to claim 3, wherein tapes having a same width are rubbed each other with the tapes positioned in a width direction.
 8. The surface treatment method for a tape according to claim 4, wherein tapes having a same width are rubbed each other with the tapes positioned in a width direction.
 9. The surface treatment method for a tape according to claim 1, wherein the tapes traveling on one line are rubbed each other.
 10. The surface treatment method for a tape according to claim 2, wherein the tapes traveling on one line are rubbed each other.
 11. The surface treatment method for a tape according to claim 3, wherein the tapes traveling on one line are rubbed each other.
 12. The surface treatment method for a tape according to claim 4, wherein the tapes traveling on one line are rubbed each other.
 13. The surface treatment method for a tape according to claim 5, wherein the tapes traveling on one line are rubbed each other.
 14. The surface treatment method for a tape according to claim 6, wherein the tapes traveling on one line are rubbed each other.
 15. The surface treatment method for a tape according to claim 7, wherein the tapes traveling on one line are rubbed each other.
 16. The surface treatment method for a tape according to claim 8, wherein the tapes traveling on one line are rubbed each other.
 17. The surface treatment method for a tape according to claim 1, wherein the tapes traveling on another line are rubbed each other.
 18. The surface treatment method for a tape according to claim 2, wherein the tapes traveling on another line are rubbed each other.
 19. The surface treatment method for a tape according to claim 3, wherein the tapes traveling on another line are rubbed each other.
 20. The surface treatment method for a tape according to claim 4, wherein the tapes traveling on another line are rubbed each other.
 21. The surface treatment method for a tape according to claim 5, wherein the tapes traveling on another line are rubbed each other.
 22. The surface treatment method for a tape according to claim 6, wherein the tapes traveling on another line are rubbed each other.
 23. The surface treatment method for a tape according to claim 7, wherein the tapes traveling on another line are rubbed each other.
 24. The surface treatment method for a tape according to claim 8, wherein the tapes traveling on another line are rubbed each other.
 25. The surface treatment method for a tape according to claim 1, further comprising: cleaning the surfaces of the rubbed tapes.
 26. The surface treatment method for a tape according to claim 2, further comprising: cleaning the surfaces of the rubbed tapes.
 27. The surface treatment method for a tape according to claim 3, further comprising: cleaning the surfaces of the rubbed tapes.
 28. The surface treatment method for a tape according to claim 5, further comprising: cleaning the surfaces of the rubbed tapes.
 29. The surface treatment method for a tape according to claim 9, further comprising: cleaning the surfaces of the rubbed tapes.
 30. The surface treatment method for a tape according to claim 17, further comprising: cleaning the surfaces of the rubbed tapes.
 31. A surface treatment apparatus for a tape comprising: a traveling device which makes a tape travel continuously; and a rubbing device which rubs the traveling tapes each other. 